Ethylbenzene conversion



Patented Nov. 7, 1950 ETHYLBENZENE CONVERSION Arthur P. Lien, Hammond,Ind., and David A. McCaulay, Chicago, 111., assignors to Standard OilCompany, Chicago, 111., a corporation of Indiana Application August 25,1948, Serial No. 46,137

This invention relates to a process for the disproportionation ofethylbenzene to produce benzene and C10 aromatic hydrocarbons. Moreparticularly, this invention is concerned with a proc- 6 Claims. (Cl.260-672) is displaced to the left, so that when appreciable quantitiesof benzene are produced or present,- very little diethylbenzene isformed. This is illustrated by an experiment in which 3.0 moles 01' essfor the conversion of ethylbenzene in high 5 benzene and 1.5 moles ofdiethylbenzene were yields to meta-diethylbenzene. maintained at 205-210F. for 3.0 hours in the We have made the observation thatethylbenpresence of A1013. The original diethylbenzene zene undergoesdisproportionation with surpriswas more than half converted toethylbenzene ining ease in the presence of liquid hydrogen fluothisexperiment. Y ride and BF: to produce chiefly benzene and Through theproper use of the BFa-HF catalyst, metwdiethylbenzeng v we can obtain avery rapid reaction at ordinary One object 01' our invention is toprovide a atmospheric temperatures and are able to shift process for thedlsproportionation of ethylben the thermodynamic equilibrium, depictedabove. zene. Another object of our invention is to proto effect asubstantially quantitative conversion vide a process for the preparationof meta-diof ethylbenzene into meta-diethylbenzene and ethylbenzene.Still another object of our invenbenzene. This is illustrated by thefollowing extion is to provide a. process for the preparation ample. ofmeta-dithylbenzene wherein the catalyst EXAMPLE functions also as aselective solvent for the metad o y e These nd o her objects of our Thereaction system comprised a BFa storage invention will become apparentfrom the ensucylinder, a BFs metering flask, and a reaction ingdescription thereof. flask individually valved to a manifold of copperWe have found that ethylbenzene can be distubin which was suitablyattached to anevacuap p o in the Presence of liquid hydrogen tion pump.A pressure gage was also attached to fluoride and BF; in accordance withthe follow- 5 the copper manifold line. Liquid hydrogen flu in equation:ride, 114.5 g. (5.725 mols), and ethylbenzene (B. P.=136 C.; n =1.4954),44 g. (0.415 mol), were introduced into the reaction flask. The HF +31,flask was then attached to the vacuum system, its 4. contents frozendown with liquid nitrogen, the

0,3, whole system evacuated and the valve to the vacuum pump closed.Boron fluoride was then and that the benzene produced in the reaction ispassed into the system from the storage cylinder substantially insolublein the liquid hydrogen and allowed to fill the metering flask. The valvefluoride and BF: whereas;the meta-diethylben of the reaction flaskwasthen opened and increzene is preferentially dissolved in the liquidhyments of BFs to a total of 25 g. were condensed I drogenfluoride-boron fluoride catalyst phase. in the reaction flask. After theaddition of each Any unreacted ethylbenzene is insoluble in theincrement of BFa, the valve of the BFa metering acid phase. flask wasclosed and the reaction flask was al- It is well known in the art thatFriedel-Crafts 40 lowed to warm to 0 C. in a water-ice bath,agicatalysts will activate the disproportionation of tated and allowedto come to equilibrium and the ethylbenzene. However, it is also knownthat pressure read on the gage. The following data when catalysts 01'this type are used the equiwere thus obtained:

' Table we BF| gg gfg Mols BF: in Moliractio Partial Press. of ad ed(g.) (in. 01mg) liq. BF; in liq. BF; (in. of Hg) 1 Pressure was Hg atstart. On shaking for 15 minutes at 0 C. it gradually fell to 17.5" Hg.llbrium for the reaction, The mol fraction of BF; was plotted against cm55 its partial pressure, as shown in the figure. From the figure, it canbe calculated that 0.207 mol of cm BF: were required in he hydrocarboncomplex, which is exactly 0 -half the number of mols of 01H ethylbenzenecharged. The HP and BF: were flashed from the reaction mixture and theresid ual hydrocarbon layer was fractionated in a wire gauze-packedcolumn (equivalent to 30 plates) and found to have the followingcomposition:

Volume Mol per per cent cont B an mm: as 40 E thy] hem mna 5 5Dietliylbenzcne 67 55 appears to be contrary to the product distributionpredicted by previous information concerning the equilibrium constant.It can be explained, however, upon the basis that diethylbenzene forms acomplex with BF: and HE (containing one mole of BF: per mole ofdiethylbenzene), that this com plex is selectively soluble in thehydrogen fluoride layer and is thus removed from further reaction andthe ethylbenzene disproportionation equilibrium is thereby shifted. tothe right. In more precise language, the equilibrium constant for theacid phase reaction is many hundred times greater than the equilibriumconstant for the hydrocarbon phase reaction.

In the ethylbenzene disproportionation reaction, we employ at leastabout 0.3 mol, preferably approximately 0.5 mol, of BF3 per mol ofethylbenzene in the charging stock; if less is used substantiallyquantitative conversion will not be attained. More than 0.5 mol of BF'sper mol of ethylbenzene may be employed if desired. In general, a molarexcess of liquid hydrogen fluoride may be employed in carrying out thedisproportionation of ethylbenzene. hydrogen fluoride concentration maybe varied between about and about 500 volume percent based on thecharging stock, we prefer to employ between about 50 and about 300volume percent. The disproportionation reaction may be efiected in thepresence of unreactive hydrocarbons, e.g.,

Although the saturated hydrocarbons, such as butane, pentanes, hexanes,octanes, cyclopentane, methylcyclopentane, dimethylcyclopentane, hexane,methylcyclohexane, saturated naphthas and the like, these beingessentially insoluble in the liquid hydrogen fluoride-B1 3 employed asthe catalyst and solvent medium'for the C10 aromatic hydrocarbonsproduced in the disproportionation of ethylbenzene. Benzene and tolueneare substantially insoluble in liquid HF-BF; under our reactionconditions and may likewise be employed as unreactive diluents.

The disproportionation of ethylbenzene may be effected at temperaturesbetween about 0 F. and about 175 F. or even higher, preferably at about30 F. to about 150 F.

In carrying out the process, the ethylbenzene charging stock, alone orin admixture with unreactive hydrocarbons may be intimately contactedwith the HF-BFa catalyst by conventional contacting or agitating meansunder a pressure suflicient at least to maintain the liquid phase,

and the reaction mixture withdrawn to a settling zone, centrifuge Or thelike to separate a raflinate layer containing said unreactivehydrocarbons, benzene produced in the disproportionation operation andunconverted ethylbenzene, and an acid layer containing liquid hydrogenfluoride,

. 4 BFa, and diethylbenzene. The hydrogen fluoride and BF: can bedistilled or flashed from the acid layer and reused in thedisproportionation operation and the residual hydrocarbons separatedfrom the acid layer can be subjected to purification treatments such asfractional distillation, washing with water or alkaline solutions, orother conventional methods of removing fluorides. The raflinate layermay be stripped of HF and BF; which are returned to the ethylbenzenedisproportionation operation.

The diethylbenzene produced is substantially one isomer, namelymeta-diethylbenzene, which is valuable as a pure chemical and especiallyvaluable as a motor fuel component, as will appear from the followingtable from which its octane number is compared with that ofethylbenzene.

OFR-R Octane No.

Meta-diethylbenzene has the highest known CPR-R blending octane numberof any dialkylbenzene. It is obvious, also, that meta-diethyllfeenzenecan be used as a component of safety uel.

Having thus described our invention, what we claim is:

1. A process for the disproportionation of ethylbenzene to producemeta-diethylbenzene in a quantit in substantial excess of thethermodynamic equilibrium quantity,- which process comprises contactinethylbenzene in the absence of other reactive hydrocarbons with at leastabout 10 volume percent of liquid hydrogen fluoride and with at leastabout 0.3 mol of BFs per mol of ethylbenzene at a temperature betweenabout 0 F. and about 175 F..under a pressure suflicient at least tomaintain a liquid phase and separating benzene and meta-diethylbenzenefrom the reaction products.

2. A process for the disproportionation of ethylbenzene which comprisescontacting ethylbenzene in the absence of other reactive hydrocarbons ina reaction zone with at least about 10 volume percent of liquid hydrogenfluoride and with at least about 0.3 mol of BFc per mol of ethylbenzeneat a temperature between about 0 F. and about 175 F. under a pressuresufficient at least to maintain a liquid phase, with drawing at least aportion of the reactionmixtui-e to a settling'zone, withdrawing fromsaid settling zone a solution comprising hydrogen fluoride,

3. The process of claim 2 wherein at least 7,

about 0.5 mol of BFs is maintained in the reaction zone per mol ofethylbenzene charged.

4. A process for the disproportionation of ethylbenzene which comprisescontacting ethylbenzene in the absence of other reactive hydrocarbons ina reaction zone with at least about 10 volume percent of liquid hydrogenfluoride and with at least about 0.3 mol of BFs per mol of ethylbenzeneat a temperature between about 0 F. and about F. under a pressuresufficient at least to maintain a liquid phase, withdrawing at least aportion of the reaction mixture to a settling zone, separatelywithdrawing from said settling zone a hydrocarbon layer comprisingbenzene and a solution comprising hydrogen fluoride, BF: andmeta-diethylbenzene. and separately recovering benzene from saidhydrocarbon layer and meta-diethylbenzene from said solution.

5. The process of claim 4 wherein about 0.5 mol of BF: is maintained inthe reaction zone per mol of ethylbenzene charged and the reactiontemperature is between about 30 F. and about 150 F.

6. A process for the substantially quantitative disproportionation ofethylbenzene to produce benzene and meta-diethylbenzene to thesubstantial exclusion or other diethylbenzenes, which process comprisescontacting ethylbenzene in the absence of other reactive hydrocarbons,with between about 50 and about 300 volume percent of liquid hydrogenfluoride and with between'about 0.3 and about 0.5 mol of BF: per mol ofethylbenzene at a temperature between 30 and 150 F. under a pressuresuflicient at least to maintain a liquid phase, allowing at least a,portion of the reaction mixture to settle to produce a hydrocarbon layercomprisin benzene and a solution comprising hydrogen fluoride, BF: andmeta-diethylbenzene, and separately recovering benzene from saidhydrocarbon layer and meta-diethylbenzene from said solution.

' AR'IHUR'P. LIEN.

DAVID A. McCAULAY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

1. A PROCESS FOR THE DISPROPORTIONATION OF ETHYLBENZENE TO PRODUCEMETA-DIETHYLBENZENE IN A QUANTITY IN SUBSTANTIAL EXCESS OF THETHERMODYNAMIC EQUILIBRIUM QUANTITY, WHICH PROCESS COMPRISES CONTACTINGETHYLBENZENE IN THE ABSENCE OF OTHER REACTIVE HYDROCARBONS WIHT AT LEASTABOUT 10 VOLUME PERCENT OF LIQUID HYDROGEN FLUORIDE AND WITH AT LEASTABOUT 0.3 MOL OF BF3 PER MOL OF ETHYLBENZENE AT A TEMPERATURE BETWEENABOUT 0*F. AND ABOUT 175*F. UNDER A PRESSURE SUFFICIENT AT LEAST TOMAINTAIN A LIQUID PHASE AND SEPARATING BENZENE AND META-DIETHYLBENZENEFROM THE REACTION PRODUCTS.